Before domestically grown fruit may be shipped to certain foreign countries (e.g., Japan), the quarantine procedures established by the receiving country must be adhered to. These quarantine procedures vary with the type of fruit being shipped and with the ultimate destination, but each procedure calls for fumigation of the fruit prior to shipment.
Fumigation of the fruit typically occurs in a packing house similar to that schematically represented in FIG. 1. The packing house may be an enclosed-wall structure, or may be formed of a skeletal framework to which quarantine netting (similar to screen door material) is secured. Such packing houses are quite large, often exceeding 10,000 square feet in floor space and requiring as many as 60 workers.
Recently harvested fruit, called "field run" fruit, is delivered to the packing house either from an immediately adjoining orchard or from a relatively nearby orchard. The delivered fruit is normally housed within bulk storage bins capable of carrying 400 pounds or more of fruit.
The storage bins bearing fruit enter the packing house through an incoming air lock of double-door design, and then are placed directly into a fumigation chamber integral with the packing house. Certain fruit (e.g., apples) must be heated prior to fumigation. Thus, the fumigation chamber is equipped with a heating source. While the storage bins may be stacked several levels high within the chamber, certain countries place restrictions on the percentage of fumigation chamber volume that may be occupied during the fumigation process. For example, Japanese procedures mandate that no more than 50% of the fumigation chamber volume be occupied.
Once the chamber is loaded, the door to the fumigation chamber is closed and the fumigation process is conducted by introducing and circulating a mixture of air and methyl bromide gas throughout the chamber for a period of approximately two hours. The rate of circulation is such that a complete air exchange occurs approximately every 4-5 minutes.
At the beginning of the fumigation cycle, all entrances to the packing house are closed and the interior of the packing house is fogged with a food-grade insecticide (e.g., pyrethrin). Fogging takes approximately 15-20 minutes. Thereafter, a short spray of insecticide is emitted approximately every two hours. After the fogging process is completed, the packing house is classified as a "quarantine secure area."
Upon completion of the fumigation process, off-gassing is conducted. The door to the fumigation chamber is opened and the mixture of air and methyl bromide gas contained therein is vented through an exhaust stack coupled to the fumigation chamber. Venting directly to the atmosphere, using fresh air drawn into the chamber from the interior of the packing house, continues for a period of time sufficient to lower the methyl bromide exposure concentration level to 5 ppm, the currently recognized level established by the Environmental Protection Agency. Off-gassing typically takes four or more hours to complete.
After off-gassing, the storage bins are transported to a bin dump which deposits the fruit atop a fruit conveyor. Once positioned upon the fruit conveyor, the fruit next encounters a series of cluster cutters. Certain fruit (e.g., cherries) may come with two or more pieces of fruit connected together by their stems. The cluster cutters, which essentially are saw blades, are used to effect a separation so that each piece of fruit stands alone with a single stem. With many types of fruit, the cluster cutters are not employed (e.g., apples, nectarines, etc.).
The fruit is next conveyed to a grading area where defective fruit is removed and discarded. While the degree of defective fruit varies considerably, it is not unusual for 10% or more of the incoming fruit to be removed at the grading area. Graded fruit then enters a sizing area located at the terminal end of the fruit conveyor, at which point the flow of fruit is split into groups of different sizes. Each group of sized fruit is placed on one of a series of "runout" conveyors disposed adjacent the sizing area. For certain fruit (e.g., cherries), in-line hydrocooling is performed while the sized fruit travels along the runout conveyors.
At the terminal end of the runout conveyors, or so-called "packing area," the sized fruit is deposited within the bottom portions of conventional shipping boxes that are positioned atop automated volume fillers. When a preset weight is achieved within a box, the automated volume filler stops the associated runout conveyor until the fully loaded box is removed and an empty box is placed in position. As shown in FIGS. 2-4, conventional shipping boxes are of corrugated configuration and are composed of cardboard. For fruits that emit heat due to the maturing process during extended shipping periods (e.g., apples), a conventional shipping box having vents and screens must be employed to disseminate the buildup of heat and to prevent insect reinfestation (see FIG. 3).
The loaded shipping boxes are next placed on a box conveyor which transports the boxes past an inspection area to a box taper. At the inspection area, an authorized inspector takes a random sample to ensure that no quarantine pests exist and that the fruit is of the proper grade and size. Usually, a 1% sample is drawn. Beyond the inspection area, the top portion (or cover) of a conventional shipping box is placed over the bottom portion containing the fruit. A band of tape is then secured across the upper surface of this top portion of the conventional box at the box taper. The tape does not secure the two halves of the box together--it simply provides identification information relating to the packed fruit.
The packed fruit then travels to a palletizing area located at the terminal end of the box conveyor, the boxes of fruit being stacked to form pallets of manageable size. The fully loaded pallets are sent to a pallet netting area, where each pallet is placed on a rotating platform. A spool of plastic stretch-wrap netting, having holes formed in it which allow air to flow through, is wound around the exterior of the rotating pallet in a spiral fashion to produce a secured pallet that maintains its structural integrity during shipment. Alternatively, corner boards held in place by strapping may be used to secure the fully loaded pallets.
Secured pallets are removed from the packing house through an outgoing air lock of double-door design. As with the incoming air lock, this double-door design prevents airborne insects from entering the interior of the packing house. Pallets exiting the outgoing air lock may then be loaded directly onto shipping containers (e.g., railway, truck, etc.) or may be deposited into an adjoining cold storage area, from which they later will be shipped. Because certain fruit (e.g., apples) must be subjected to forced-air cooling prior to shipment, the cold storage area must possess this capability.
Fumigating fruit using the above-described packing house is generically represented in the process flow diagram of FIG. 5. All harvested fruit is directed to the fumigation chamber where "bulk fumigation" is conducted. This process is known as bulk fumigation because each and every piece of fruit is fumigated. The fumigated fruit is then graded and sized by packing house workers, and subsequently packed for shipment in conventional shipping boxes of corrugated cardboard design.
While quarantine treatment of fruit may be generically represented by FIG. 5, it must be noted that each particular fruit requires its own unique processing. Processing of cherries is represented in FIG. 6 (refer additionally to FIG. 1). As indicated, harvested cherries stored in open-top bins are directed to the fumigation chamber where bulk fumigation of the cherries is conducted. At the conclusion of the off-gassing cycle, the cherries are placed upon a fruit conveyor and transported to cluster cutters, where separation of connected cherries is effected. Downstream along this conveyor, the cherries are graded, sized, and transferred to a plurality of runout conveyors.
Along the runout conveyors the cherries are exposed to in-line hydrocooling to bring about a 34.degree. F. core temperature. In the packing area, the bottom portion of a non-vented conventional shipping box of corrugated design is pre-lined with a plastic bag. The bag and box combination qualifies as a "quarantine-certified shipping box" for the shipment of cherries. The bag and box are then filled with fruit as the box sits atop the automated volume filler. When full, the top of the plastic bag is folded inwardly on itself and the box is placed on a box conveyor. If selected, the box is pulled from the box conveyor for inspection. If not, the box continues along the box conveyor to an area where a shipping box cover is applied and identifying tape is placed over the cover. The packed boxes are then palletized, pallet netting is applied, and the secured fully loaded pallets are then transported from the packing house to the cold storage area for storage and/or shipment.
With certain fruits, such as apples, there are no currently accepted quarantine procedures for many foreign countries. Thus, the shipment of apples to these foreign countries simply does not occur. However, there is a "proposed" quarantine procedure using current technology for sending apples to Japan, which is illustrated in FIG. 7. This procedure is quite similar to that for cherries illustrated in FIG. 6, but does have several important differences. First, prior to bulk fumigation, the apples must undergo 55 days of cold treatment, wherein a core temperature of approximately 34.degree. F. or below (but not freezing) is maintained. Second, the apples must be heated to a core temperature of 10.degree. C. (50.degree. F.) or above prior to commencement of the bulk fumigation procedure. This heating step is normally accomplished within the packing house's fumigation chamber. Third, apples require no in-line hydrocooling prior to being packed. Fourth, apples must be packed in screened/vented conventional shipping boxes to allow the buildup of heat during shipment to be disseminated. Lastly, apples must be forced-air cooled in the cold storage area to approximately 34.degree. F. core temperature prior to being shipped.
The above-described bulk fumigation approach to fumigating fruit is problematic. As stated, 10% or more of the incoming fruit may be culled at the grading area. Furthermore, only a fraction (perhaps 25%) of the fruit leaving the sizing area is of a quality sufficient to be sent to the foreign country imposing quarantine (fumigation) procedures. Consequently, the fumigated fruit not of sufficient quality must be sold in domestic markets at steep discounts. Because quarantine procedures do not apply to fruit grown and sold domestically, domestic markets simply are not very interested in fruit that has been fumigated.
The disadvantages of bulk fumigation do not stop here. Unnecessarily fumigating fruit means that higher amounts of methyl bromide are vented to the environment. It also means that packing house workers handling the fruit are exposed to more methyl bromide than is necessary. Furthermore, there currently are state and federal governmental efforts under way to completely eliminate exposure of workers to methyl bromide.
It has been suggested that fruit bound for foreign countries imposing quarantine procedures simply be graded and sized prior to fumigation. This way, only that fruit meeting the foreign standards need be fumigated. Unfortunately, this approach means that the fruit entering the packing house would be graded and sorted twice. Not only is this handling labor intensive, additional damage to the fruit is also caused. Accordingly, industry has declined to use this approach, opting instead for bulk fumigation.
It also has been suggested that "in-box fumigation" could overcome many of the problems associated with existing procedures. In-box fumigation requires that the fruit be packed, fumigated, and shipped in the same container. However, currently existing containers and procedures will not allow for in-box fumigation.
As shown in FIG. 4, a conventional shipping box of corrugated design has a plurality of flutes formed between opposing walls of the box. During fumigation, these flutes are filled with methyl bromide gas. During the off-gassing period, much of the methyl bromide gas remains trapped in these flutes. Thus, because the allowable exposure level of 5 ppm cannot efficiently be reached during the off-gassing process, conventional shipping boxes have not been approved as a quarantine-certified packaging material for in-box fumigation. An additional drawback of conventional shipping boxes of cardboard composition is that they do not retain structural integrity during extended shipping periods (due to moisture accumulation, etc.).
While containers formed of plastic and wood may technically qualify as quarantine-certified packaging materials, they possess other disadvantages. Plastic is much more expensive to produce than cardboard and would prohibitively add to the cost of fruit shipped in such containers. Further, the additional weight of a plastic container is undesirable. As for wood containers, the porous nature of wood does allow migration of methyl bromide through it, which results in essentially no retention of methyl bromide gas at the conclusion of the off-gassing period. However, this same porous nature provides a container that is susceptible to reinfestation during shipment.
As described above, current procedures for the fumigation of fruit are fraught with limitations and associated problems. This invention is directed to overcoming these problems.